Extensible-collapsible structure



Dec. 17, 1968 P. E DOHgT 3,416,170

EXTENS IBLE-COLLAPSIBLE STRUCTURE Filed Aug. 5, 1966 4 Sheets-Sheet 1 PIERRE E.DOH ET BYMFZAA/ ATTORNEY 5 17, 1968 P. E. DOHET EXTENSIBLE-COLLAPSIBLE STRUCTURE 4 Sheets-Sheet 2 INVENTOR Filed Aug. 3, 1966 ATTORNEY Dec. 17, 1968 P. E. DOHET 3,416,170

EXTENSIBLE-COLLAPSIBLE STRUCTURE Filed Aug. 5, 1966 I 4 Sheets-Sheet s m n .frllllunn u m HT OE I W nO D 2 m M E RE 1? M L o- N9 :25: m9 mm M 8 0V m fi w 2 ON om N fimvwwwu fiw lllll lllllllllll l l hhrhi.\\\\k ATTORNEY P. E. DOHET Dec. 17, 1968 EXTENS I BLE-COLLAPS IBLB STRUCTURE 4 SheetsShee t 4 PIERRE EDOHET ATTORNEYS United States Patent 3,416,170 EXTENSIBLE-COLLAPSIBLE STRUCTURE Pierre E. Dohet, 208 S. Lee St., Alexandria, Va. 22314 Filed Aug. 3, 1966, Ser. No. 569,869 16 Claims. (Cl. 9-2) ABSTRACT OF THE DISCLOSURE An occupiable structure has a pair of rigid end members linked by a flexible skin or sheet coextensive with the edges of the end members so that the structure may be repeatedly extended and collapsed. Rigid beams operating in a chord compression system are employed to erect the structure from a collapsed state, or vice versa, each beam pivotally fastened to an end member such that its free extremity would describe an arc were it not for the presence on the opposite end member of an intercepting channel along a chord of that arc, the channel arranged to accept a spring-loaded pin at the extremity of the beam. As each beam is pushed or otherwise moved into the erecting condition its associated pin slides within the channel against the force of the loading spring and ultimately locks into position in the channel thereby to latch the beam. Each beam supports a portion of the flexible sheet, which is incapable of self-support, to impart to it a curvature maintaining substantial continuity of contour with that of the rigid end members.

The present invention relates generally to structures which may be rapidly erected and collapsed, and more particularly, to structures adapted for occupation and which may be rapidly and reliably erected from a collapsed semiflexible form to a relatively rigid form of substantially precisely defined and dimensioned shape and cross-section, and correspondingly rapidly collapsed into a compact state for ease and convenience of transport and/ or storage when not in use.

In its broader aspects, the invention, in concept, principles, and practice, is applicable to the manufacture or assembly and use of any occupiable structure which is desired to be imparted with the attributes and characteristics of a mechanism capable of quick and convenient stowage in a compact mass or form and equally rapid and convenient extension or erection to a predetermined substantially rigid form or shape. Hence, the present invention is particularly useful and suitable for such purposes as collapsible shelters or collapsible vessels, for example. Accordingly, while the description and illustration of a preferred embodiment of the invention will be directed toward a collapsible boat, it is to be emphasized that no restrictions or limitations are intended or are to be placed on the scope or application of the invention thereby. Rather, any limitations or restrictions on the present invention are to be determined solely from the definition of invention as recited in the appended claims.

In the past, many varieties of collapsible structures, such as collapsible boats, have been provided wherein the structure is composed of a large number of separable parts which are assembled or disassembled, as required, to alternatively erect and store the structure. Beyond such disadvantages as the ease with which the component parts may be lost or misplaced, these structures typically require relatively lengthy periods of construction and disassembly, depending upon number of pieces and overall size, which operate to partially defeat the intended purpose of portability, i.e., the contemplated ease and convenience of compact transport and storage in the collapsed state. The aforementioned disadvantage of extensive periods required for erection and for collapse is also found in those prior art structures of one piece flexible or semiflexible construction, composed of several permanently fastened members, along with the greater disadvantage of difliculty of maintaining precisely defined form or shape of the extended unit after repeated erection and collapse operations. The term collapse, as used in the context of the present application, means intentional breaking down or folding together of the parts of the structure into compact form.

It is a principal object of the present invention to pro vide a collapsible structure of semirigid or semiflexible character composed of several permanently fastened parts which are arranged in such cooperative relationship as to render the structure rapidly erectable (or extensible) and collapsible, as desired, and capable of maintaining its precisely defined erected form or shape despite repeated extending and folding thereof.

Briefly, in accordance with the present invention, controlled longitudinal extension is provided in any structure of folding characteristics by means of a compensated chord compression system or mechanism. In essence, a suitable structure is provided with a pair of rigid end or side sections, and a rigid mid-section having a dimension, along the line joining the centers of the two rigid end or side sections (i.e., the longitudinal dimension), much less than the distance separating those two rigid ends. Securely fastened to the rigid mid-section and each end section, and coextensive therewith at the junctures, is a sheet of flexible material of sufiicient thickness and integrity of construction to meet the demands of structural reliability, durability and strength imposed by the intended use of the structure. Since each pair of rigid sections is connected by a flexible sheet or skin, the structure may be folded so that the rigid ends are positioned within or immediately adjacent the rigid mid-section, being separated only by the folds of the flexible material. The rigid parts of the structure, i.e., the ends or sides and mid-section, are provided with respective shapes suitable to the intended use of the extended or erected final structure. This advantageous arrangement and relationship of component parts of the structure does not alone, however, solve the problems of providing rapid erection and collapse capabilities with maintenance of precisely defined and dimensioned shape and cross-section, which have plagued the prior art attempts to produce extensible-collapsible structures. A simple and etfective solution is mani fested, according to a principal feature of the present invention. by the provision of additional rigid structural members or beams pivotally fastened to either section of each confronting pair of the aforementioned rigid components of the structure and operable in a compensated chord compression arrangement to stiffen and to desirably and precisely shape the flexible portions of the structure upon extension thereof. Briefly, compensated chord compression is effected by use of a structural member or beam arranged to rotate or pivot freely about a fixed point at one of its extremities, the other extremity being adapted to mechanically intercept a selected chord of the arc which it would otherwise describe during rotation. As rotation of the beam is pursued beyond the point of interception and through a means for restricting the motion of the free end or extremity of the beam to a path along said chord, separation of the rigid section at which the rotation or pivot point of the beam is located and the rigid section at which the chord-defining means is located is achieved by a distance equal to the radius of the aforementioned are less the height of the segment bounded by the arc and the chord. In this manner, a precise tension and shape may be created and maintained in the flexible material between any two rigid sections. The chord-defining device may simply be a channel adapted to accept and restrict the otherwise arcuate movement of a springloaded pin or arm located at the extremity of the structural member or beam remote from the aforementioned pivot or rotation point thereof. Suitable latching means may be provided along the chord-defining channel to prevent return of the beam after erection, and suitable tripping means located thereat to enable instantaneous release of the structural member when it is desired to collapse the structure for stowing. Several such structural members and associated chord defining, latching, and release members or mechanisms are provided to impart the desirable tension and continuity of shape to the flexible material between rigid members.

In the specific but exemplary case of a collapsible boat fabricated in accordance with the principles of the present invention, rigid bow, stern, and mid-section members or portions are provided, with respective continuous sheets of flexible material fastened to and between the bow and mid-section members at the forward end and between the mid-section and stern members at the aft end. Each flexible sheet is coextensive, along its fastened edges, with the cross-section of the rigid member at the respective line of attachment or fastening. Pivotal beams are provided in the form of gunwales (gunnels) rotatably secured to the fore and aft ends of the deck or upper end of the mid-section, at both starboard and port sides thereof, and cooperating chord-defining, latching and releasing means secured to respective points on the rigid bow and stern members. Beams of similar construction and operation to that of the gunwales are utilized as keelson members to produce tension and shaping of the bottom of the vessel in conformity with the proper contour of the underwater profile in sheer plan. such beams functioning in corresponding fashion to the gunwales but at the interior of the bottom of the boat along the center thereof.

Accordingly, it is a further object of the present invention to provide extensible-collapsible structures having rigid sections, each adjacent pair of which is connected by a cross-sectional coextensive flexible skin which is tensioned and shaped, upon extension of the structure, by beam members pivotally secured to either of the rigid sections and operating under the principle of compensated chord compression.

Still another object of the invention is to provide an erectable-collapsible boat having rigid bow, stern and midsection portions separated by flexible material fastened thereto, so that the bow and stem portions may be folded into the mid-section portion when the boat is collapsed, and further having structural members pivotally fastened to one or more of the rigid portions and cooperative with associated movement restricting, latching and releasing members on the respectively confronting rigid section to provide proper tensioning and shaping of the flexible material upon of the boat.

The above and still further objects, features and attendant advantages of the present invention will become apparent from a consideration of the following detailed description of an exemplary embodiment therof, especially when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of an extensible-collapsible boat constructed in accordance with the principles of the present invention;

FIGURE 2 is a plan in the extended state;

FIGURE 3 is a sectional view taken along the lines 3-3 of FIGURE 2;

FIGURE 4 is a detailed plan view illustrating the structure and operation of a pivotal beam member and associated chordal path-defining device of the boat of FIGURE 1',

FIGURE 5 is a sectional view taken along the lines 5--5 of FIGURE 3;

FIGURE 6 is a fragmentary sectional view taken along the lines 6 6 of FIGURE 3;

view of the boat of FIGURE 1 FIGURE 7 is a plan view of the boat of FIGURE 1 in the collapsed state;

FIGURE 8 is a sectional view taken along the lines 8-8 of FIGURE 7;

FIGURE 9 is a detailed perspective view illustrating the structure and cooperation between the spring-loaded pin or arm of the pivotal beam member and the chordal path-defining member with associated latch and release mechanisms.

FIGURE 10 is a sectional view taken along the lines 1il10 of FIGURE 9;

FIGURE 11 is a perspective view illustrating in detail the universal joint pivotal coupling of each keelson member; and

FIGURE 12 is a sectional view of the seat-retaining mechanism taken along the lines 12-12 of FIGURE 2.

One example of an extensible-collapsible structure embodying the concepts of the present invention is a vessel for navigating the water, such as the dinghy shown in the accompanying drawings. The description of the boat will proceed with general reference to the several figures, and with specific reference to a particular figure when greater clarity is required.

In general, the boat comprises three rigid sections constituting a bow portion 10, a stern portion 11, and a midsection portion 12. Each of these sections or portions is constructed and shaped in accordance with known principles of boat building and naval architecture so that in the extended or erected condition the boat constitutes a craft whose shape and dimensions conform to a specific table of off-sets for selected stations from bow to stern. Each of bow, stern and mid-section portions are watertight members which may be formed from any suitable material, fiberglass, aluminum, magnesium and wood being representative examples; and bow and stern portions 10 and 11 are preferably hollow to render the boat lighter in weight and to enhance the buoyancy characteristics and strength thereof. Mid-section portion 12 is a curved sheet of the selected rigid material, and includes a pair of ribs 15 and 16 extending transverse to the longitudinal axis or center line of the boat and projecting upwardly toward the interior of the craft along the fore and aft ends of the mid-section portion.

Securely fastened to the bow, stern and mid-section portions within runways 20 offset from and along the underside of the craft at edges of adjacent confronting ends of those portions (FIGURE 3) are a pair of sheets of flexible material 23 and 25 which permit folding of the bow and stern portions 10 and 11 into mid-section portion 12 (FIGURE 7). Each of sheets 23 and 25 may, for example, be composed of several layers or plies of high tensile strength fabric, such as closely woven nylon cord, impregnated, separated and completely covered with synthetic rubber or vinyl. A wide choice of suitable materials will be apparent, consistent with the requirements of durability, flexibility, strength, light weight, water-tight construction, and resistance to solar radiation and salt water, of each sheet. Both sheet 23, which extends between bow section 10 and the forward end of mid-section 12, and sheet 25, which extends between the aft end of mid-section 12 and stem section 11, may be permanently fastened in coextensive relationship with the crosssectional edges of the respective sections along the line of attachment (runway 20) by bonding with any suitable heavy duty marine cement or waterproof epoxy resin, for example.

Rotatably coupled to midsection portion 12 by pivot pins 30, 31, 32 and 33 at recessed corners 28, forward and aft, port and starboard, respectively, are four gunwales, the forward pair being designated by reference numeral 35 and the aft pair by numeral 37. Each of the gunwales comprises a rigid structural member or beam having a pair of substantially parallel walls 40 and 41 (FIGURES 3, 5 and 6) bridged along the edges which are to be disposed interiorly of the boat (when deployed) by a connecting portion 43, and open in spaced relationship to form 'a slot at the edges disposed along the exterior of the boat.

Slot 45 in each of the gunwales is adapted to accept or to accommodate a free edge of the flexible sheet between the rigid sections or portions with which the respective gunwale is associated. For example, forward port gunwale 35, shown more clearly in FIGURE 6, is constructed to permit entry of a free edge of flexible sheet 23 via its slot 45. Each free edge of each sheet is preferably reinforced by a nonextensible, high tensile strength wire or cord 50, of Dacron or stainless steel, for example, to substantially reduce the possibility of application of excessive or unnecessary force to that free edge during deployment of the craft. The non-extensible wire or cord may be retained in position by a bonded loop, formed along the free edge of the sheet as shown in FIGURE 5, or may be physically included between the surfaces of the flexible skin or sheet. In either event, the wire or cord is positioned, when the boat is deployed (extended), to form the chord 53 (FIGURE 2) of the curve conforming to the deck line, in a plane parallel or substantially parallel to that of the waterlines.

A downwardly extending lip 53 (FIGURES 5 and 6) along the edge of lower wall 41 of each gunwale is utilized to provide smooth continuous surface contact with the flexible sheet to prevent the existence of severe stresses which would be present if the sheet were wrapped about the edge of a thin wall, and to aid, when the gunwale is extended, in creating and maintaining a precise amount of tension in the flexible sheet or skin.

In order to further control the degree of tension in the flexible sheet, each gunwale is provided with a springloaded fitting in the form of an arm or pin 56 (FIG- URES 2, 4, 9) having a ball or roller 58 at the exposed end thereof and coupled at the other end to a compression spring 60 within hole 62 extending partly into the end of the gunwale remote from its pivot point and along an axis parallel or substantially parallel to the chord 53 to be formed by nonextensible wire 50 when the boat is deployed.

Fastened along recessed areas 65 on the deck of bow portion 10 and recessed areas 66 on the deck of stem portion 11, in a symmetrical arrangement relative to the axis or center line of the deployed boat, are four channel members, designated by reference numeral 68 in the forward area and by reference numeral 69 in the aft area, each channel member being associated with a distinct and different one of the gunwales. As shown more clearly in FIGURE 4, in the absence of a channel member, the ball 58 of the spring-loaded fitting of each gunwale describes an are 70 as the gunwale is rotated about its pivot point at the respective upper corner of the mid-section portion 12. Each channel member (such as member 68 shown in FIGURE 9), however, is arranged to accept the respective ball 58 within its channel 72 at end 73 thereof, so as to restrict the path of the ball, as the respective gunwale is pivoted, to the chord 75 (FIGURE 4) of are 70 in the compensated chord compression technique described above. Such movement of the ball along the respective channel is permitted, of course, by the spring-loading of the fitting of which the ball is a part.

The end of each channel member 68 (or 69) opposite the end 73 into which the ball 58 is inserted is provided with a latch and release mechanism for the spring loaded fitting, in the form of a bracket 78 pivotal about a pin 79 (FIGURES 9 and 10) and having a shape, at the end 80 thereof closest the channel and remote from insertion point 73, conforming to the shape of ball member 58. The remote end of the channel member is also provided, by appropriate machining, with a surface having a shape conforming to the shape of the ball member. A compression spring 82 is provided between bracket end 83 and the upper surface of the channel member to permit end 80 to pivot upwardly, as ball 58 is forced to the limit of its path through channel 72, and thence to return to its normal position, when the ball is seated Within the conforming surfaces at the end of the channel member. Release of the ball 58, and thus of its associated gunwale, is effected by application of a downward force on bracket end 83, transmitted by the hand of the boat erector, for example, together with a force on the ball applied via the respective gunwale in a direction parallel to the axis of channel 72 toward opening 73 thereof.

To further control the tension in the flexible sheet or skin and to impart the desirable continuity of shape to conform to the predetermined cross-section of the craft at various selected stations between tip of how and Stern (according to a predetermined table of offsets, well known in the boat building art) and as well to conform to the proper contour of the underwater profile of the craft in the sheer plan thereof, there is provided a pair of keelson members 85 and 86 (FIGURES 2 and 3) in the form of rigid beams having functional and operational characteristics corresponding to those of the gunwales.

In this particular case, the keelsons 85 and 86 are provided with pivotal couplings in the form of universal joints (such as shown in FIGURE 11) at the bottom center of the side of bow portion 10 in confronting relationship with mid-section portion 12 and at the bottom center of the side of stern portion 11 in confronting relation to the opposite end of mid-section portion 12. Spring loaded fittings generally designated by reference numeral 90 are provided in each of the keelson members 85 and 86 at the respective end remote from the pivot point in a manner identical to that previously described for the gunwals. Separate channel members 92 are arranged at either side of the center line of the boat at each end of mid-section portion 12 respectively confronting the bow and stern portions along the interior of the bottom of the mid-section adjacent ribs 15 and 16, respectively. Channel members 92 are identical in all respects, including the latching and releasing mechanism, to the previously described channel members 68 and 69. The seat for the ball of the spring-loaded fitting of each keelson member in respective channel members 92 is aligned along the axis or center line of the craft.

Disposed on and supported by each of keelson members 85 and 86, pads in the bow and stern sections, and ledges outside the midsection ribs, are a pair of rigid floor sections or floor boards 94 and 95. Each of the floor sections is composed of a pair of panels, 97 and 98 for floor section 94, and 99 and 100 for floor section 95, hinged at their respective junctures coincident with the center line of the craft (FIGURES 1, 2, 4, and 5). Consistent with accepted boat building practice, the floorboards need not be secured firmly to the hull, but may, if desired, simply rely on locators on the underside of each board and on gravity for retention in proper position when the boat is in use. When the dinghy is to be collapsed, the floor sections 94 and are simply lifted out and folded prior to proceeding in the manner to be described. Each panel of each floor section is, of course, shaped to conform to the respective interior curve of the boat in the plane of that floor section when the boat is deployed and to accommodate any parts such as channel members 92 which might otherwise interfere with proper placement of the floor sections.

The bottom of each keelson member 85 and 86, as viewed in FIGURES 3 and 5, for example, is shaped such that when the spring-loaded fitting thereof is in com pression, and the flexible sheet or skin is therefore in tension, the flexible skin conforms to the proper contour of the underwater profile of the craft in sheer plan.

The craft is also provided with a set 102, for an oarsman or other occupant or occupants, preferably in the form of a rectangular sheet of rigid material which may be of the same type as that used for the other rigid sections of the boat. The seat 102 is provided with a lineal pivot by a downwardly extending bracket 103 having a hole extending therethrough for acceptance of a shaft or rod 105. Shaft 105 is provided with spring loaded projections 107 at either end thereof, which fit into mating holes in brackets 110 positioned and secured at either interior side of mid-section 12. As indicated in FIGURE 2, the shaft extends traversely to the centerline of the craft and is positioned at approximately the midpoint thereof. Hence, seat 102 may be pivoted from a vertical or upright position to a horizontal position for seating occupants of the boat. In order to support the seat in a horizontal position when the boat is deployed, a pair of struts 113 and 114, preferably of tubular aluminum, are provided at their respective outermost extremities with pins 118 (FIGURE which mate with respective 'holes in brackets 117 at either side of rib 15, and welded at the innermost extremities, with a cradle member 119 having right-angled flanges at 120 and 121. The flanges are separated by a distance sufficient to accommodate the width of seat 102.

Locking of the seat in the horizontal position is provided by a spring-loaded twistable pin arrangement 125 at the flanged end of each strut, shown more clearly in FIGURE 12. The pin 126 is pushed into a mating hole 127 in seat 102 after which shaft 120 is twisted via a ring 130 to force a projection or tip 131 into a locked position interiorly of cup 133. The projection 131 is accepted within cup 133 via a channel (not shown) in a conventional manner, and once rotated into a locked position, is maintained there by the compressed spring 135. Seat locking and releasing mechanisms 125 are provided on both strut members 113 and 114. When the struts have been set up and the seat locked, the ends of the struts adjacent the rib brackets 117 are forced outwardly thereagainst so that they are maintained in position for supporting the anticipated weight of occupants to be seated on seat 102. When the seat is unlocked, however, by twisting and releasing pins 126 from mating holes 127 and pivoting the seat toward an upright position, the single welded structure of struts 113 and 114 and cradle member 119 is pivoted about the axis defined by pins 118 to a lowered position (FIGURE 8).

A separate keel or skeg 140 may be attached to the craft by insertion of a pin 143 in the forward end thereof into a mating slot in permanently fastened bracket 145 projecting from the center of the underside of mid-section portion 12, and then fastening the other end of the skeg into channels of a permanently fastened member 150 projecting centrally from the bottom of stern portion 11 by means of a pair of thumbscrews 151 (FIGURE 3). Some play is preferably present in the skeg, consistent with the slight play in the other members. The skeg, of course, permits the craft to be navigated in a reasonably stnaight course. Oar-locks (not shown) may be provided at the gunwale pivot points for rowing the dinghy.

It will readily be observed from the foregoing description that when the boat is collapsed for stowing or transportation the entire assemblage of secured components is readily stored within the space defined by the midsection portion 12 as shown in FIGURES 7 and 8. If, in addition, seat 102 is pivotally fastened, as shown in FIG- URES 3, 5 and 8, to the downwardly projecting bracket 103 via a single swaged pin or rivet 152, the seat may be swiveled from an upright position to a lowered vertical position (FIGURE 8) so that it, too, is stored within the confines of mid-section portion 12.

When the boat is to be extended, i.e., erected, each of the bow and stem portions are pulled from the midsection portions, thus carrying along or unfolding the previously folded flexible sheet portions therewith. The non-extensible wires or cords 50 in the free edges of the flexible sheet are securely fastened, as by riveting, to the respective corners of the bow, stern and mid-section portions, and as the boat is extended are inserted into the channels of the respective gunwales during rotating of the gunwale about its pivot point. The spring-loaded fittings of the gunwale and keelson members are inserted into the respective channel members and locked therein in the manner previously described and the floor sections then unfolded into deployed position. The seat is then swiveled in two directions into a horizontal position and locked. It will thus be seen that the boat may be extended quite rapidly, under three minutes in practice by even an inexperienced crew, and may be collapsed, when desired, in correspondingly rapid fashion. Of course, the particular steps in the process of extending the boat may be varied as desired, consistent with the requirement that the bow and stern portions 10 and 11 be removed from the mid-section portion 12 as the first step of the procedure. Similar considerations apply to the collapsing of the boat.

Since substantially all of the members of the structure are permanently fastened together, there is no danger of loss of one or more components during breakdown, storage or transportation. Moreover, the compactness and light weight of the collapsed structure admits of particular ease and convenience of handling by a single person.

A semicircular ring lock 159 (FIGURE 3) may be molded or bonded along the center line of how section 10 for attachment of a ring 160, to permit fastening of a painter, i.e., tie line (not shown), for docking purposes when the boat is in use.

Exemplary approximate dimensions of a boat constructed in accordance with the present invention are as follows:

Overall length (deployed) 7'4" Overall length (collapsed) 2'-0" Bow section 10 length Bow section 10 width (aft) 2'-l" Bow section 10 depth (aft) 1'2% Mid-section 12 length 2'4)" Mid-section 12 width (fore) 3'-7%" Mid-section 12 width (aft) 3-9%" Mid-section 12 depth (fore) 15% Mid-section 12 depth (aft) l'5 /s" Stern section 11 length 0'9" Stern section 11 width (fore) 2'l0" Stern section 11 depth (fore) 1'2%" Forward gunwales Length (extended and compressed) 24%" Compression 0'-1 /s Effective track length (channel) 0'-5 A" Aft gunwales- Length (extended and compressed) 23 /2" Compression 0'1 A;

Effective track length (channel) 0 6% Keelson (fore and aft)- Radius of horizontal revolution 1'-1l%" Compression 0--l Effective track length (channel) 0'7% The above dimensions are furnished purely by way of example and are in no sense to be considered as limitations of the invention. Feasible sizes and shapes of structures constructed in accordance with the present invention will, of course, to a great extent depend upon the specific type of structure involved. It will be observed, for example, that rapidly erectable and collapsible shelters or other enclosures may utilize the principles set forth herein.

From the foregoing description, it will be observed that structures in accordance with the present invention, While collapsible, are eflective to maintain a high degree of strength and rigidity along with continuity of shape throughout When in the extended condition. Moreover, each edge of each flexible portion of the structure is either permanently fastened to a rigid section or is provided with a reinforcing non-extensible cord by which sl1ppage or collapse of the structure, except as initiated by the user When the structure is to be stored or transported, is overcome.

The present invention thus provides a mechanical system by which rigidity is rapidly imparted to an initially semiflexible or semirigid structure formed from solid sections linked by flexible skin of adequate strength to meet the demands of intended use, the rigid structure being developed by an extension process which takes advantage of the revolution of a plurality of beams operating in a chord compression system, as described. The chord compression technique is itself characterized by several advantages, includingthe following:

Provision of a solid rigid structure from two or more rigid sections linked by flexible material; positive locking of the rigid sections and tensionining of the flexible material therebetween; provision of appropriate form and shape of the flexible material in predetermined simple and compound curves; and maintenance of the shaping of the flxible skin without need for any mechanism apart from that constituting a permanently secured member of the structure.

The present invention is further characterized by the extreme simplicity of erection and stowage of a collapsible structure by the substantial elimination of intermedate framing required between rigid sections to impart to flexible material interposed therebetween the curvatures inherently provided by the extremities of the adjacent rigid sections.

While the chord compression system as described above in detail is preferrer, other types of extensible-collapsible support or beam arrangements will be apparent to those skilled in the art to which my invention petains from a consideration of the foregoing description. For example, each of the beams (gunwales and keelsons) may be pivotally secured to the respective rigid sections (bow and mid-section and stern) which they are to separate when the craft is deployed, and hinged at a substantially centrally located point along the respective beam. Such an arrangement would permit each beam to fold at the hinge point and to pivot or rotate about the point at which it is secured to the rigid sections, when the boat is to be collapsed. Similarly, deployment of the boat would involve extension of each beam from its folded position to continuous support position capable of withstanding the forces of compression thereon. Preferably, a conventional locking-unlocking device would be employed at the hinge point to prevent folding of the beam except when the boat is to be intentionally collapsed.

Another suitable arrangement similar to that described immediately above, is to provide centrally hinged beam members which are pivotally secured to only one rigid section and which are provided at the other extremity (i.e., the normally free end) with any conventional member appropriate for coupling with a mating member secured to the respective opposing rigid section. Such an arrangement would permit one end of each beam to be freed from a rigid section when the boat is to be collapsed, after which the beam would be folded for stowage.

Still another appropriate variation of the chord compression system for the beam members, resides in the provision of a completely rigid beam pivotally coupled to one rigid section and having at its free extremity a ball or roller member to be engaged by a respective channel member mounted on the other rigid section. Unlike the system disclosed in the detailed description, however, the channel member is spring loaded to permit the ball or roller to move along an arc therein and to be locked in the deployed position. Alternatively, neither ball member nor channel member is spring loaded but the channel member is fabricated with an arcuate channel and suitable locking and releasing device for the ball or roller of the beam. In the latter arrangement, loading of each beam in compression is accomplished by the flexible and partially resilient character of the skin between the rigid section.

I claim:

1. An extensible-collapsible structure, comprising at least a pair of rigid members having preformed shapes conforming to the intended use of the structure when extended; a sheet of flexible material linking said rigid members and fastened thereto adjacent portions of the rigid members which are to be in confronting relationship when said structure is extended, said sheet being coextensive with said portions; and releasable means for separating said rigid members in locked extended configuration by a distance suflicient to place said flexible sheet .in tension therebetween, and for supporting said sheet along preselected portions therof in predefined curves to .maintain substantial continuity of contour between said rigid members and said sheet when said structure is extended, wherein said means includes:

a pair of rigid beams each pivotally coupled to one of either of said rigid members and each shaped to supply at least one of said predetermined curves to the supported sheet,

each of said beams having a spring-loaded arm at the extremity thereof remote from its pivotal coupling point, and

means disposed on the rigid member other than that to which the respective beam is pivotally coupled for engaging the free end of said arm and for restricting the motion thereof, during pivoting of the respective beam, to a path constituting the chord of an arc which said free end of said arm would otherwise describe.

2. The invention according to claim 1 wherein is included means for latching each arm to lock the respective beam in predetermined position when said structure is extended.

3. The invention according to claim 2 wherein is included means for releasing each arm from the latched position to unlock the respective beam when said structure is to be collapsed.

4. The invention according to claim 1 wherein each of said beams is provided with means for accepting and supporting the nonfastened edges of said sheet in one of said predefined curves.

5. The invention according to claim 4 wherein each of said nonfastened edges of said sheet is reinforced by a non-resilient cord fastened at its ends to the rigid members linked by said sheet.

6. The invention according to claim 4 wherein is provided at least one further beam pivotally coupled to one of said rigid members, and having a spring-loaded arm cooperating with an arm-accepting and 'motion restricting means disposed on the opposite rigid member, to provide additional support and tensioning of a portion of said flexible sheet between said nonfastened edges.

7. The invention according to claim 6 wherein is further provided means for latching and for releasing the springloaded arms of said beams to permit locking of said beams in predetermined position, during extension, and unlocking therefrom, during collapse.

8. The invention according to claim 1 wherein said rigid members have shapes and dimensions to permit one of said rigid members to be accommodated within the other of said rigid members when said structure is collapsed.

9. The invention according to claim 7 wherein said structure is a boat having at least three of said rigid members, said three rigid members constituting bow, midsection and stern portions of said boat, said bow and said mid-section portions having said sheet of flexible material fastened therebetween and said mid-section and stem portions having a further sheet of flexible material fastened therebetween in corresponding manner, the first-named pair of rigid beams respectively pivotally fastened to deckline corners of one of said bow and mid-section portions, another pair of rigid beams respectively pivotally coupled to deckline corners of one of said mid-section and stern portions, said first-named and said another pair of beams operating as gunwales, and a pair of said further rigid beams respectively pivotally coupled to and operating as keelson members along the center line of the bottom of said boat between said bow and mid-section portions and between said mid-section and stern portions thereof, each of said beams having associated therewith a respective arm-accepting and motion restricting means secured to the rigid member confronting that to which the respective beam is pivotally coupled.

10. The invention according to claim 9 wherein each nonfastened edge of each of said flexible sheets is reinforced by a nonextensible cord fastened at its ends to the rigid sections linked by the respective flexible sheet.

11. The invention according to claim 9 wherein each of said bow, midsection and stern portions have shapes and dimensions to permit said bow and stern portions to be housed within said mid-section portion when said boat is collapsed.

12. The invention according to claim 10 wherein said gunwales are provided with slots for accepting said reinforced nonfastened edges for secure retention thereof when said gunwales are in the locked position.

13. The combination according to claim 12 wherein said boat is further provided with a flat seat for occupants, said seat being independently pivotally coupled for pivoting about two orthogonal axes, one of said axes along a shaft extending transverse to the centerline of said boat within said mid-section portion thereof, and the other of saidaxes along a shaft extending perpendicular to the first-named shaft, said first-named shaft extending through a bracket by which the second-named shaft is coupled to said seat.

14. An occupiable structure of extensible-collapsible construction, comprising:

A pair of rigid members having preformed shapes conforming to the intended use of the structure when extended; 1

a sheet of flexible material linking said rigid members and fastened thereto adjacent portions of the rigid members which are to be in confronting relationship when said structure is extended, said sheet being coextensive with said portions; and

means for separating said rigid members in locked extended configuration by a distance sufficient to place said flexible sheet in tension therebetween, and for supporting said sheet along preselected portions thereof in predefined curves to maintain substantial continuity of contour between said rigid members and said sheet when said structure is extended, said means including:

a channel member on one of said rigid members, means engageable in and cooperating with said channel member to restrict the extension of said structure along a predetermined path while continuously increasing the forces on said sheet to correspondingly produce increased tension therein; and

locking means for retaining said extension restricting means in engagement with said channel member, absent forcible release therefrom, when a predetermined degree of tension has been achieved on said sheet together with support thereof in conformance with said continuity of contour.

15. The invention according to claim 14 wherein one of said channel member and said extension restricting means is spring loaded.

16. An extensible-collapsible sea-going craft comprising:

three rigid members constituting a rigid bow, a rigid stern, and a rigid mid-section;

respective continuous watertight sheets of flexible material fastened to and between the bow and mid-section at the forward end and the mid-section and stern at the aft end, each sheet being coextensive along its fastened edges with the cross-section of each of the respective ones of said rigid members at the line of fastening thereto;

a plurality of respective pivotal beams for spanning each of said sheets between said rigid members to maintain a predetermined fixed separation between said rigid members sufiicient to place said sheets in tension, while supporting said sheets to maintain continuity of contour with said rigid members, when extended;

said beams rotatably secured to a respective one of said rigid members whose attached sheet they are to span, at points directly opposite the adjacent one of said rigid members; and

means on the respective adjacent one of said rigid members for separably engaging said beams to maintain said craft in locked extended configuration, and to permit release of said beams when it is desired that said craft be collapsed.

References Cited UNITED STATES PATENTS 2,405,627 8/ 1946 Williams l5049 2,790,978 5/1957 Tigreit 15049 X 1,937,729 12/ 1933 Straussler 92 2,346,081 4/ 1944 Randrup 9-2 2,636,192 4/1953 May 9-2 3,028,612 4/ 1962 Sindell 9-2 MHJTON BUCHLER, Primary Examiner.

R. A. DORNON, Assistant Examiner.

US. Cl. X.R. -4 

